My new Ram 3500 SWD QC has anti spin option. The tech at the dealer said it work differently than ones I am accustomed to in the when the wheels are off the ground if you spin one side the other goes the other way. This to me was always a dead give away that the rear was a peg leg or the sure grip (can we please use this Mopar term?)was fried. I am more from a Mopar muscle car background but have finally landed my dream truck. Any techs in this forum that can explain. My service manuals are on order.

 

If that's true, then they've not only managed to duplicate the test results of a 'peg leg' but the traction as well.

I have the anti-spin and it's worthless, as near as I can tell. My daughter's Acura RSX, our old Taurus, and my Ranger 4x4 in 2wd all went through snow that this truck couldn't.

 

cp,
Sorry to hear your anti-spin is worthless. Mine works very well . You just have to remember the diff gears can only transfer the amount of torque (or some multiple there of) being consumed by the spinning tire to the non or less spinning tire. That means if one tire is on ice and is spinning very freely then only a very small amount of torque is transfered to the non-spinning wheel. That small amount of torque may not even move the tire. But, simple fix is to make the spinning tire consume more torque. How? Step lightly on the emegency brake. Spinning tire now has to consume torque to spin against the brake and the diff gears transferrs more torque to the non-spinning tire. Result, off you go!

The Boss Hog
(I didn't grow up in Colorado for nothing . . . )

 

I'll have to give that a try the next time I get stuck in this thing. That should be fairly soon, as we've got a lot of winter left. I did add some railroad ties to the bed so we'll see if that helps any.

My positrac memories go back to a 1966 Chevy 2wd pickup that had it. That thing was fantastic--you couldn't hardly get the thing stuck. That is why I opted out of 4x4 on this truck. For the few times a year I could use 4wd, it just isn't worth the extra cost and mileage loss. However, if Dodge used hubs, I probably would have given 4x4 a lot more consideration.

 

ppsi
The anti-spin in the new Rams is completely different from the old sure grip. It is call "Trac-Rite" and here is the description from the service manual:

DESCRIPTION
The Trac-Rite™ differential is a helical gear differential.
The differential has two side gears, six pinion
gears and six pinion brake shoes.

OPERATION
When one wheel begins to spin the pinion gears on
that side are forced toward the pinion brake shoes.
The pinion brake shoes then cause frictional drag on
the opposite pinion gears and the side gear. These
friction forces transfer the power to the opposite
wheel. Once the frictional forces are overcome, differentiation
will occur. The torque will be continually
biased by the frictional forces to the high traction
wheel.

The Boss Hog
(Hope this helps . . . )

 

cp,
I would suggest giving it a try before you get stuck It will also work on an open differential. Try putting one wheel in a muddy ditch and the other wheel on dry pavement. If you just put it in gear and floor it, the wheel in the ditch will just sit and spin. But do the same thing while lightly applying the emergency brake and it will pull right out

The Boss Hog
(I got a 4x4 because of the snow in Florida . . . )

 

You never know.... it could happen. And when it does, you'll be ready for it!!

 

I think the term "snow" has a totally different meaning in FL (at least it used to).

 

Only hard core off roaders & drag racers want a true posi trak.
If you remember the muscle car era those cars hooked up great in a straight line, the problem came when you wanted to actulally turn a corner.
They would drag one tire around since they move at diffrent speeds, I can remember tires squeeling going slowly around a corner!!

I know my limited slip is working by the 2 black patches my truck leaves at stop lights!!
There has to be a trade off between being able to pull your boat out of a slippery loading ramp & being able to turn a corner without squealing tires.

I did notice that my 03 has anti spin & my 97 Dakota had sure grip, I haven't noticed any diffrence between them myself.

 

The Boss Hog,

OPERATION
When one wheel begins to spin the pinion gears on
that side are forced toward the pinion brake shoes.
The pinion brake shoes then cause frictional drag on
the opposite pinion gears and the side gear. These
friction forces transfer the power to the opposite
wheel. Once the frictional forces are overcome, differentiation
will occur. The torque will be continually
biased by the frictional forces to the high traction
wheel.

I'm wondering if this description is for another model? AAM says this is an all gear system and from looking at the pictures I can't see any clutches. The description posted would be perfect for the old Track Lock system with clutch discs behind the spider gears. Hmmm. Any thoughts? If they do have "pinion brake shoes" there may be wear issues and the lube will probably affect the performance.

Wetspirit

 

None, that is the description right out of the Service Manual (page 3-145).

Actually IMO they could have used a better term than "pinon brake shoes" although I can see how they came up with it. Other helical gear limited slip units have pinion gears that push against the differntial case. Trac-Rite uses helical pinion gears but adds a "thrust-bushing-spacer-pad-spin-stopper" (my term ) to the end on the pinion gears. When the pinion gears push against them, they tend to slow down the relative spin of the pairs of pinion gears. Relative spin/twist between helical pairs is what forces them outward. They are not wear items like the clutch packs were but provide a smoother action when transferring torque.


The Boss Hog
( . . . . . . . . )

 

So, in the general opinion of those who have looked at the operation are these going to work welll for a long time or be a PIA engineers idea of a good thing? Not the engineer being a PIA but a poor working axle would be a PIA.

 

The Boss hog,

So instead of the locking action coming from conventional spiders trying to escape from each other and pressing on a clutch pack, the force is from a helical gear moving along it's axle and pressing on a thrust washer. Right? Somewhere in the literature I read (can't remember where) that the system was based on the Gleason Torsen design where power can be transmitted from a pinion to a bull gear in a worm system but cannot be transmitted from a bull gear to a pinion in the same system. With a little friction on the end of the helical gear in this design a large amount of differential resistance can be obtained. I'm still looking at it and wishing I had one apart to study closer.
To test mine I jacked one rear wheel off the ground and blocked the front wheels. Then put it in drive, and the lifted wheel spun. With the slightest brake application, the wheel on pavement spun too. That is plenty agressive for normal use. I also feel it locking up on turns with a little throttle, and slipping the inside wheel. Not spinning it but locking them together. I think this is a very good system for general conditions short of all out rock climbing. And much less strain on things than an ARB.

Wetspirit

 

An excellent way to test/demonstrate the differential action And as one member said, unless you are a hard core off roader, it works fine and will last a long time.

The Boss Hog
(Pssst . . . Wetsprit, check my pictures to see my FXDX )

 

The Boss Hog,

Nice scoot! One of the two best Harley models ever made in my humble opinion. Looks like Screamin Eagle heads. Is it a 1550? Nice header too, does it make it hard to check the oil when hot?

Wetspirit